There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Probability Distributions.- Linear Models for Regression.- Linear Models for Classification.- Neural Networks.- Kernel Methods.- Sparse Kernel Machines.- Graphical Models.- Mixture Models and EM.- Approximate Inference.- Sampling Methods.- Continuous Latent Variables.- Sequential Data.- Combining Models.

Pattern Recognition and Machine Learning

Geant4 is a software toolkit for the simulation of the passage of particles through matter. It is used by a large number of experiments and projects in a variety of application domains, including high energy physics, astrophysics and space science, medical physics and radiation protection. Its functionality and modeling capabilities continue to be extended, while its performance is enhanced. An overview of recent developments in diverse areas of the toolkit is presented. These include performance optimization for complex setups; improvements for the propagation in fields; new options for event biasing; and additions and improvements in geometry, physics processes and interactive capabilities

/pdf/geant4-developments-and-applications-3ff6jy0cfx.pdf

Geant4 developments and applications

(Abridged) The Large Area Telescope (Fermi/LAT, hereafter LAT), the primary instrument on the Fermi Gamma-ray Space Telescope (Fermi) mission, is an imaging, wide field-of-view, high-energy gamma-ray telescope, covering the energy range from below 20 MeV to more than 300 GeV. This paper describes the LAT, its pre-flight expected performance, and summarizes the key science objectives that will be addressed. On-orbit performance will be presented in detail in a subsequent paper. The LAT is a pair-conversion telescope with a precision tracker and calorimeter, each consisting of a 4x4 array of 16 modules, a segmented anticoincidence detector that covers the tracker array, and a programmable trigger and data acquisition system. Each tracker module has a vertical stack of 18 x,y tracking planes, including two layers (x and y) of single-sided silicon strip detectors and high-Z converter material (tungsten) per tray. Every calorimeter module has 96 CsI(Tl) crystals, arranged in an 8 layer hodoscopic configuration with a total depth of 8.6 radiation lengths. The aspect ratio of the tracker (height/width) is 0.4 allowing a large field-of-view (2.4 sr). Data obtained with the LAT are intended to (i) permit rapid notification of high-energy gamma-ray bursts (GRBs) and transients and facilitate monitoring of variable sources, (ii) yield an extensive catalog of several thousand high-energy sources obtained from an all-sky survey, (iii) measure spectra from 20 MeV to more than 50 GeV for several hundred sources, (iv) localize point sources to 0.3 - 2 arc minutes, (v) map and obtain spectra of extended sources such as SNRs, molecular clouds, and nearby galaxies, (vi) measure the diffuse isotropic gamma-ray background up to TeV energies, and (vii) explore the discovery space for dark matter.

The Large Area Telescope on the Fermi Gamma-ray Space Telescope Mission

Polyphenols are secondary metabolites of plants and are generally involved in defense against ultraviolet radiation or aggression by pathogens. In the last decade, there has been much interest in the potential health benefits of dietary plant polyphenols as antioxidant. Epidemiological studies and associated meta-analyses strongly suggest that long term consumption of diets rich in plant polyphenols offer protection against development of cancers, cardiovascular diseases, diabetes, osteoporosis and neurodegenerative diseases. Here we present knowledge about the biological effects of plant polyphenols in the context of relevance to human health.

/pdf/plant-polyphenols-as-dietary-antioxidants-in-human-health-29nh0evfx2.pdf

Plant Polyphenols as Dietary Antioxidants in Human Health and Disease

http://manuscript.elsevier.com/S0048969722019854/pdf/S0048969722019854.pdf

Differential Quercus spp. pollen-particulate matter interaction is dependent on geographical areas.

The 2BN bremsstrahlung cross section is a well-adapted distribution to describe the radiative processes at low-electron kinetic energy (E(k) < 500 keV). In this work a method to implement this distribution in a Monte Carlo generator is developed.

A new low-energy bremsstrahlung generator for GEANT4.

The Clear-PEM system is a prototype scanner for Positron Emission Mammography (PEM), currently under development. In the scope of this project, we have implemented three iterative algorithms for 2D image reconstruction, using linograms: the Algebraic Reconstruction Technique (ART), the Maximum Likelihood – Expectation Maximization (ML-EM) and the Ordered Subsets – Expectation Maximization (OS-EM) algorithms. All these algorithms require the calculation of a system matrix, which contains the information about the probability of a pair of photons being the product of an annihilation occurred in a certain voxel of the object.
In this paper, we present three different methods that we have developed (the pixel-driven, the ray-driven and the tube-driven method) to calculate the system matrix. The comparison of these methods was done with the help of Monte Carlo simulated data, which allowed evaluating image spatial resolution, convergence speed and image uniformity.
The results showed that the tube-driven method allowed the best image spatial resolution and the best values of the homogeneous index calculated, with any of the image reconstruction algorithm. These results strongly recommend the use of this system matrix in future works in which we will compare the image reconstruction algorithms regarding the lesion detectability with data simulated using a digital breast phantom.

System Matrix Calculation for 2D Image Reconstruction Algorithms for the Clear-PEM Scanner

The present work assesses different Monte Carlo methods in radiative heat transfer problems, in terms of accuracy and computational cost. Achieving a high scalability on numerous CPUs with the conventional forward Monte Carlo method is not straightforward. The Emission-based Reciprocity Monte Carlo Method (ERM) allows to treat each mesh point independently from the others with a local monitoring of the statistical error, becoming a perfect candidate for high-scalability. ERM is however penalized by a slow statistical convergence in cold absorbing regions. This limitation has been overcome by an Optimized ERM (OERM) using a frequency distribution function based on the emission distribution at the maximum temperature of the system. Another approach to enhance the convergence is the use of low-discrepancy sampling. The obtained Quasi-Monte Carlo method is combined with OERM. The efficiency of the considered Monte-Carlo methods are compared. NOMENCLATURE DNS Direct Numerical Simulation FM Forward Method I Radiative intensity [W sr −1 m −2 ]

Comparison Of Monte Carlo Methods Efficiency To Solve Radiative Energy Transfer In High Fidelity Unsteady 3D Simulations

/pdf/comparison-of-monte-carlo-methods-efficiency-to-solve-4c6su9ai3y.pdf

Pedro Rodrigues

Papers

Differential Quercus spp. pollen-particulate matter interaction is dependent on geographical areas.

A new low-energy bremsstrahlung generator for GEANT4.

System Matrix Calculation for 2D Image Reconstruction Algorithms for the Clear-PEM Scanner

Comparison Of Monte Carlo Methods Efficiency To Solve Radiative Energy Transfer In High Fidelity Unsteady 3D Simulations

Comparison of Monte Carlo Methods Efficiency to Solve Radiative Energy Transfer in High Fidelity Unsteady 3D Simulations